Display screen or a portion thereof with a graphical user interface



The sole FIGURE is a front view of a display screen or portion thereof with a graphical user interface showing our new design.

The broken line perimeter represents both the boundaries of the display screen and the graphical user interface. This outer edge of the portion of the display screen is understood to be congruent with the outer edge of the graphical user interface. The broken lines shown in the drawings illustrate portions of the display screen or a portion thereof with a graphical user interface that forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or a portion thereof with a graphical user interface, as shown and described. 